Process of making refractory linings



Oct. 13, 1931. s. WESTBEG ,827,446

PROCESS OF MAKING REFRACTORY LININGS Filed Aug] 14, 1928 Patented Oct. 13, 1931 1,827,446'

UNITED STATESPATENT OFFICE SIG'URD WESTBERG, OF OSLO, NORWAY rnocnss OF iuAKING REFRACTORY L'nmos Application filed August 14, 1928, Serial No. 299577; and in Germany April 26, 1928.

This invention relates to a process for makand durable refractory lining is of great' iming refractory linings and is particularlyuseportance. v i ful in lining metallurgical furnaces, crucbles Thedifiiculties mentioned occur not only and the like. It is peculiarly adapted to the with iron, steel or other metals and alloys'of liningof induction furnaces, and I will, -"h1gher melting points, but also with non-fer- 55 therefore, disclose the invention as applied rous metals such as highly cupriferous alloys, to this use, although it should be understood loaded bronzes, and other ordinary commerthat it is not necessarily limited to this field. clal alloys. In fact, with many metals and V Before proceeding to a .description of the alloys the inducti'on furnace so far has been :30 invention and an'enumeration of its objects not only economically questionable, but also and advantages, it is desired to refer to some techncally impossible. of the difl'culties which have to be overcome With the fo'regoing in mind, the primar'y in making satisfactory refractory linngs. ob ects of my invention will be better under-` For example, in melting metals or alloys in stood and may be said to involve the provi-' an induction furnace, the lining -is'subjected son .of a refractory lining which, while still not only to the chemically COITOSlVe influence i of very reasonable depth or thickness, is far of sla-gs, metals, 'gases or vapors, but also to more durable, effective as an insulation, imthe erosiveor scouring'efect 'of the molten perv'ous and che mically resist'ant than, herecharge which is given a whirling motion by tofore. The invention also aims to make pos the electromagnetic action. sible the use of larger induction furnaces with Furthermore, 'in coreless induction fura marked decrease in their hazard, i as well naces, whether of high, medium or low freas to extend the variety of metals'and .alloys quency, it is very important to have the linwhich can be treated therein. ing as thin as possible in order to secure good It-s also an'object of my invention to pro- 5 coupling and high efliciency. vde a process of making refractory linin s In addition, the great drop in temperature whereby a much higher temperature can e between'the highly heated interier and the air employed in baking the liningthan will be or water cooled induction coil on the outside encountered when the furnace, crucible or the places exceedingly heavy stresses on the linlke s be ng used to melt a charge. The imi 3@ ing which frequently develops cracks'with -portance of ths will bebetter appreciated th i i id tal di adv ntag and often when it is recalled that in present practice I timeslserious results, such as injury .or death e' 1111111 is -sinply baked. in by the first to workmenwhere the molten bath'escapes. h g y i p e makes possi le the i Interruptins or-disturbances of this nature use of the finest refractories requring much also involve a great loss of metal and mag r b ngtemperatures than are ossible' terials as well as of time incident to the mak- Where the l g 13 to be b g y t e heat ing of repairs and suspension offo'perations. the t h g q y For all of which reasons the use of what, v fracomes have further d g otherwise, is probably an almost ideal method ductionafurnaces n that a th nner lnng can be used which will permit a reductionin the of heating has been l mited to nducton furdistance between the con and the Charge 4 naces of relatively small size and capacity The fore on 'to ethet and, even in these, the lnngs, generally, have objects as %gig m P 3 3' a compammvely' few inafter, or are'ncident to my invention, are 45 g Again, m large furnaces j obtained in the following manner, reference to workmen from any falure of 'the lnng s b i h d t th accompanyng h i g materially increased. Also, because the powhi h o h t di g ti ll 111 er necessary to maintain the heat balance, is trate two ways of employing the improved so largely dependent upon the quality. of the process. F r I J i 50 insulation, this question of a highly resistant Fig. 1 is a vertical section through an induction furnace illustrating the mamer in which I bake the lining, and Fig. 2 is a similar View showing how the invention may be applied to the baking of crucibles.

In Fig. 1 the refractory lining a of an induction furnace b may be applied, for example, by ramming, or in any other suitable or desired manner, after whch a suitable core d (preferably a hollow, graphite core) is lowered into position within the lining by any suitable suspending device e. The current is then turned on in the coil c, which, of course, induces a flow in the core d. Graphite, being very heat resistant,while, at the same time, possessing good conductivity, permits the temperature to be carr'ied to extremely high levels, thereby thoroughly baking and even glazing the inner surface of the lining. In the showing the core is free of the walls so that the transfer of heat is chiefiy by radiation, which arrangement prevents reactions with the lining material or sticking of the core. However, in some instances the core may be placed in direct contact with the lin- %y using the foregoing method, it is apparent that it is possible to employ eitremely high-refractory materials, which snter or melt at temperatures far above the working temperatures employed with the charge Any desired temperature or time for'baking are readily employed, and the thickness of the lining can be accommodated to the dimensions of the furnace and the drop in temi perature from the inside to the outside. Because the baking is from the nsde outwardly, the temperature can be forced suflicently high so that, even with Very highly refractory materials, it ispossible to obtain a meltd coating on the interiorwhch Wlll result in an unusually hard, impervious and re- 'sistant inner surface. I

The lining can be composed either of pure oxides, as, for instance, magnesia, alumina, zircon-oxide, thoroxide, silica in different sizes of grains and pre-treatment, etc., orof a mixture of oxides, silicates or compounds, which, atthe 'very high heating temperatures employed, produce new formations of crystals or compounds, such, for example, as

mrxtures of magnesium oXide and alumina to' form spinel-compounds, or of zircon oxide and thorium oxide, etc. Or, in cases where such is preferred, carbonaceous-linings can be made by adding pitch, tar, etc., or a mixture of carbides, as, for instance, silicon carbide or calcium carbide. In the same way, linings of carbon-clay-paste can also be hak ed directly in the furnace of a composition suchas used for the production of crucible steel.

With the present improvement it is possible to use the compact and resistant refractory materials which are melted and urified in the arc furnace. These can be ba ed to a mames Operations, so that no detrimental efl'ects will be encountei'ed from this source during subscquent use of the furnace or crucble.

If cracks develop in thelning after the A initial baking operation and subsequent cooling, these can be filled in with more material and the baking repeated, so'that a perfectly sound lining can be developed gradually with the inner or final layer or coating of the lining being made of some specially resistant material if desired. This latter feature, of course, saves considerable in the cost over a complete lining ofsuch ecial material. Unusuallypu-re metals can e produced in furnaces where the lining can be of such improved and resistant characteristics as are herein made possible.

Other core materials can be used such as high-fusible carbides, for example, silicon carbide, or such metals as tungsten, molybdenum, etc., in which case the baking can then be made to take place in a neutral or reducing gas or in a vacuum. several co'es might be used or a core of special shape as in Fig. 1, concentratesthe heat at the surface eter or optical thermometer to obtain an exact determination of the temperature because the instrument can be-visioned against the interior of the hollow core where substantially a black body condition prevails, the observation being made through a suitable opening in the core. In this way a, very 'exact plotrol over the temperature of firing can be With my improvement repars can be made quickly and easily by grinding or chippin out the damaged portions of the lining an then filling in with suflicent newimate'ial to again establish substantially the old contour. This can then be baked as 'previously described whereby much time' and power can be saved, since 'it is unnecessary to heat up an entire new lining.

Fig. 2 shows how ,the process can be used for the production of high-ref-acto-y crucibles.. In this application of the invention the induction coil as well as the core are movably Suspended so that the coil can be lifted above or dropped below the crcible and the of the lining and permits the use of a pyromi coil. i 9. A method accordingto claim 4 wherein core lowered thei-ein. In this way a great number of crucibles can be preform'ed and baked consecutively in the shortest possible.

time.

I claim:

1. The inductive baking 'of refrctories at temperatures materially higher than those prevailing during the use for which they are intended.

- 2. As a new article of manufacture, an inductively baked refractory.

3. As a new article of manufacture, an inductively baked refractory furnace lining.

4. The method of preparing refractories foruse in furnaces which includes baking the refractory by placing an induction coil to the outside thereof and a core on the inside, and

applying current to the coil.

5. The method of preparing refractory furnace linings which includes baking the-- lining by placing an induction' coil around the lining and a core within, and applying current to the coil,

6. The method of preparing refractory furnace linings which includes baking the lining by placin'g an induction coil around the lining and a hollow core within, and applying current to the coil. r V

'7. The method of preparing refractory furnace linings which includes baking the lining by surroundingthe furnace with an induction coil, suspending a core within the lining and ap lying current to the coil.

-8. The met od of preparing refractory furna'ce linings' which includes baking the lining by surrounding the fur-hace with an induction coil, suspending a hollow core with- V in the lining and applying current to the the core is space-,d from the refractory.

In testimony whereof I have hereunto sgned my name;

SIGURD WESTBERG. 

